The present invention relates to the fabrication of semiconductor-based devices. More particularly, the present invention relates to improved techniques for fabricating semiconductor-based devices with organo-silicate-glass.
In semiconductor-based device (e.g., integrated circuits or flat panel displays) manufacturing, dual damascene structures may be used in conjunction with copper conductor material to reduce the RC delays associated with signal propagation in aluminum based materials used in previous generation technologies. In dual damascene, instead of etching the conductor material, vias, and trenches may be etched into the dielectric material and filled with copper. The excess copper may be removed by chemical mechanical polishing (CMP) leaving copper lines connected by vias for signal transmission. To reduce the RC delays even further, low dielectric constant materials may be used. These low dielectric constant materials may include organo-silicate-glass (OSG) materials, such as Coral(trademark) and Black Diamond(trademark). OSG materials may be silicon dioxide doped with organic components such as methyl groups. OSG materials have carbon and hydrogen atoms incorporated into a silicon dioxide lattice, which lowers the dielectric constant of the material. However OSG materials may be susceptible to damage when exposed to oxygen, H2, and NH3 gases, which are used for stripping photo resist. To facilitate discussion FIG. 1 is a flow chart of an etching process of OSG materials used in the prior art. FIGS. 2A-C are schematic side views of an etched OSG according to the process of FIG. 1. An OSG layer 204 may be deposited on a substrate 208 (step 104), as shown in FIG. 2A. The substrate 208 may be a silicon wafer or another type of material or may be part of a layer over a wafer. An antireflective coating (ARC) 212 may be deposited over the OSG layer 204 (step 108). A patterned resist mask 216 may be placed over the ARC 212 (step 112). The patterned resist mask 216 has an aperture 220. The substrate 208 may be placed in an etching chamber where the OSG layer 204 is etched (step 116). A plasma dry etch may be used to etch the OSG layer 204, which forms an opening 224 under the aperture 220 in the patterned resist mask 216, as shown in FIG. 2B. Some of the patterned resist mask 216 is removed during the OSG layer etch. In addition, sidewalls 228 may be formed within the opening 224. The patterned resist mask 216 and sidewalls 228 would be simultaneously stripped (step 120). One way of simultaneously stripping the patterned resist mask 216 and sidewalls 228 is by exposing the patterned resist mask 216 to a plasma with a CF4 (or another fluorocarbon) and N2/O2, N2/H2, or N2/NH3 etchant gas. The plasma would strip both the patterned resist mask 216 and the sidewalls 228, as shown in FIG. 2C.
OSG materials may be very susceptible to damage due to the removal of organic content by exposure to the plasma used to strip the resist and sidewalls. The plasma may diffuse a few hundred angstroms into the OSG layer and cause damage 240 to the OSG layer bordering the opening 224. The ARC 212 may protect the upper OSG layer 204. Part of the damage caused by the plasma is the removal of carbon and hydrogen from the damage area causing the OSG to be more like silicon dioxide, which has a higher dielectric constant. Damage may be quantified by measuring the change in SiC/SiO ratio of the OSG layer from FTIR analysis. A decrease of 1% in SiC/SiO ratio on a blanket film of a 1 micron thickness could be very significant as the damage is limited to a few hundred angstroms on the top layer of the blanket film. When translated to the trench side wall that means a damage of a few hundred angstroms on each side of a 2000 xc3x85 trench wall.
It is desirable to reduce damage to the OSG layer.
To achieve the foregoing and other objects and in accordance with the purpose of the present invention for making an etch organo-silicate-glass (OSG) layer over a substrate is provided. Generally an OSG layer is placed over the substrate. A patterned resist mask is placed over the OSG layer. The OSG layer is then etched, where the etching of the OSG layer forms at least one opening in the OSG layer and sidewall within the at least one opening. The patterned resist mask is then stripped by a plasma. A wet stripping is then used to remove the sidewalls.
In addition, the present invention provides an etched organo-silicate-glass (OSG) layer. Generally an OSG layer is placed over the substrate. A patterned resist mask is placed over the OSG layer. The OSG layer is then etched, where the etching of the OSG layer forms at least one opening in the OSG layer and sidewall within the at least one opening. The patterned resist mask is then stripped by a plasma. A wet stripping is then used to remove the sidewalls.
These and other features of the present invention will be described in more detail below in the detailed description of the invention and in conjunction with the following figures.